Liquid level and temperature indicating apparatus



y 4, 1954 E. x. SCHMlDT 2,677,276

LIQUID LEVEL AND TEMPERATURE INDICATING APPARATUS Filed July 26, 1948 4 Sheets-Sheet 1 3'. rWQ L f z a a a a STANDARDIZE LEVEL.

OFF T TEMP.

y 4, 1954 E. x. SCHMIDT 2,677,276

LIQUID LEVEL AND TEMPERATURE INDICATING APPARATUS Filed July 26, 1948 4 Sheets$heet 2 r 4/7 n4 A llz ad 96 9/ "Wm/f 104" 9b a 90 gm; 9 a e 9P1 1 i E fiaiisii:

i v 1 I n 88- 90 9& I0 98 9 I05 [06 PIE-L May 4, 1954 Filed July 26, 1948 E. x. SCHMIDT 2,677,276

LIQUID LEVEL AND TEMPERATURE INDICATING APPARATUS 4 Sheets-Sheet 3 May 4, 1954 E. x. SCHMIDT 2,677,276

LIQUID LEVEL AND TEMPERATURE INDICATING APPARATUS Filed July 26, 1948 4 Sheets-Sheet 4 OFF T TEMP.

SENDER D- 6 RECEIVER f fit k! 60 [IL l p g. L |J CB 54 :35 G 5%;

GALVANOMETER 0R EQUIVA LBNT "P SENDERA -cA 5 STANDARDIZE LEVEL. 3 =fi00 OHMS FROM 0T0 I0. OFF T TEMP.

Is Cows l0 OHMS EAcn.

5 =10 o/ms- 0 TO 1. GA LVANOMETER R 5 0F 6 -pin. To'bCo/I... EQU'VA LBNT- R =5 or 6 i CalA. To'OCo/L. C B

Patented May 4, 1954 UNITED STATE OFFICE LIQUID LEVEL AND TEMPERATURE INDICATING APPARATUS Edwin X. Schmidt, Chenequa, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware 3 Claims.

This invention relates to an improved apparatus for distantly indicating the value of a condition; and more particularly to distant liquid level and temperature indication for tank farms and the like.

An object of the invention is to provide an indicating apparatus of the aforementioned character whereby an attendant at a distant (or common) point may readily and accurately ascertain in sequence the level and the average temperature of the liquid or liquids in each of a multiplicity of storage tanks.

Another object is to provide a liquid level indicating system comprising a sending potentiometer for each tank and a receiving potentiometer common thereto, with associated switching means for selection of the tank with respect to which the measurements are to be made at any instant, and automatically operable self-standardizing means responsive to the conditions at each particular sending station when active.

Another object is to provide such an indicating system wherein each sending station includes a resistance thermometer, a sending potentiometer positioned by a special float, and .a single dry cell for supplying current to the sending potentiometer and its associated thermometer.

Another object is to provide such a system wherein each sending station is connected to the receiving station through four wires, and wherein a null method of measurement is employed, so that no current flows through the respective wires when readings are taken, wherefore the readings are unaffected by the resistance of the connecting wires.

Another object is to provide such a system wherein the respective sending potentiometer slide wires and the common receiving potentiometer slide wire may have a total length of twenty-five feet or more; the receiving potentiometer being provided with an indicator scale operable throughout the entire range of movement of the receiving potentiometer slide wire brush, the indication on which scale can easily Another object is to provide floats of novel form for positioning the respective sending potentiometers in such a manner as to properly indicate the actual level of the liquid in each tank regardless of differences or changes in density of the liquid or liquids within the respective tanks in which they float.

Another object is to provide a thermometer of novel form whereby the average temperature of the entire body of liquid in each tank may be accurately ascertained and indicated.

Another and more specific object is to provide such a thermometer comprising a fine nickel wire, which is enclosed with a reinforcing spring wire within a flexible protective tubing formed of a suitable synthetic plastic, one end of which tubing is attached to the tank bottom, and the other end of which is attached to a float of suitable size; whereby the reinforcing spring acts to substantially equalize the disposition of the thermometer between the bottom of the tank and the upper surface of the liquid.

Another object is to provide a system whereby from liquid level indication, strapping tables, and temperature correction tables for the particular liquids in the respective tanks, the actual liquid content of each tank may readily be calculated.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate an embodiment of my invention which will now be described; it being understood that the embodiment illustrated is susceptible of modification, in respect of certain structural details thereof, Without departing from the scope of the appended claims.

In the drawings, Figure 1 is a schematic and diagrammatic illustration of a liquid level and temperature measuring and indicating system as applied to a multiplicity of tanks for liquids, forming a so-called tank farm.

Fig. 2 is a view, partly in elevation and partly in vertical section, of one of the float units and the associated means for effecting operation of the sending potentiometer type rheostat associated therewith.

Fig. 3 is a top plan view of the float unit illustrated in Figs. 1 and 2.

Fig. 4 is a fragmentary view, partly in elevation and partly in vertical section, of the fixed elements of the sending slide wire potentiometer type rheostat and illustrating the manner in which the movable contactor is adapted, to cooperate therewith.

Fig. 5 schematically illustrates my improved thermometer resistance, and the float means associated therewith, whereby the resistance wire is substantially evenly distributed throughout the entire depth of the liquid in the tank.

Fig. 6 is a greatly enlarged view, in transverse cross section, of the aforementioned flexible plastic tubing and the insulated resistance wire and reinforcing spring wire housed within said tub- Fig. '7 illustrates diagrammatically the float, the counterweight, and the cables connected between said parts and their respective drums; certain legends being added to said figure for use in mathematical formulae hereinafter set forth.

Fig. 8 is a diagrammatic illustration of certain elements of the present device as applied to a system involving manual setting of the common receiving potentiometer rheostat and manual setting of a rheostat to be connected in parallel with said receiving potentiometer rheostat, and

Fig. 9 is a diagrammatic illustration, in greater detail, of one of the like sending potentiometer rheostats, and the receiving potentiometer rheostat common thereto.

Referring to Fig. 1, it is desired to indicate at a common oint, or single receiving station, I4 the liquid temperature and the liquid level in each of a plurality of tanks; one of which is represented by the liquid level, shown in dotted lines at 45, having the float unit associated therewith, as indicated in general by the numeral I6. A resistance type thermometer is positioned within each tank, as diagrammatically illustrated at I'l'. Other elements of the sending stations respectively associated with each of the tanks are shown more or less diagrammatically within the dotted line rectangle I; the corresponding sending stations of the other five tanks of the particular installation herein illustrated being diagrammatically illustrated by the full line rectangles designated by numerals 2, 3, 4, 5 and 6, respectively.

The float unit [6 in each tank is suspended from a cable I; said float unit being adapted to rise or fall with each change in the liquid level in its respectively associated tank. Cable 1 is so arranged as to effect, or permit, turning of a drum 8 in accordance with the fall or .rise in liquid level, through the medium of a counterweight 9 associated with float unit I6; the supporting cable I of counterweight 9 being unwound from or wound onto a drum II, which is tapered as shown to compensate for the weight of the variable length of cable i between drum 8 and the float unit I6 and the variable length of cable Ii! between drum I I and weight 9.

Rotation of drums 8 and I I effects corresponding rotation of a threaded shaft 8 which in turn effects movement of a slide wire brush or bridging contactor 8 for cooperation with the slide wire resistance, shown diagrammatically at S, forming part of a sending potentiometer.

The resistance type thermometer unit H in each tank is preferably shaped or wound to spiral form in such a manner that the coils thereof will nest within each other in a common plane upon the bottom wall of the tank, when the latter is empty. Resistance thermometer I! is preferably rigidly attached at one end to the bottom wall of the tank I8 (Fig. ),-as indicated at I9; a float 20 of suitable size being attached to the other end of thermometer Il, so that the latter will be substantially evenly distributed, throughout its length, between the bottom wall of tank I8 and the liquid level It, aforementioned.

Thermometer resistance I'i preferably comprises a suitable length of resistance material; such as a nickel wire Il of very small cross sectional area having a redetermined temperatureresistance coeificient. Resistance wire I'i is preferably in the form of a loop extending from the point I9 at the bottom wall I8 of tank IT to the point of support of the upper end portion of said loop by float 20. As shown in Fig. 6, wire Il' is provided with a suitable insulating covering or coating I'l throughout the active length thereof; whereby the arm portions of the loop are insulated from lateral contact with each other, and from contact with the reinforcing spring wire I'I Wires Ii and H are enclosed within a suitable length of flexible plastic tubing II as illustrated, thus insulating wire I'I from contact with tank I8 and from the liquid within the latter. I have obtained excellent results by using tubing I'I composed of the flexible plastic sold commercially under the trade name of Saran; although it is to be understood that tubing formed of any other flexible plastic of suitable composition might be employed.

In the potentiometer type sending unit indicated at I in Fig. 1, a battery 27 supplies current to the slidewire S and its paralleling circuit consisting of conductors 26 and 25, thermometer I1, conductors 2| and 22, resistance 23, and conductor 24. Included in the battery circuit are conductor 26, battery 21, conductor 23 and fixed resistor 29. Conductors G S and T respectively connect to the low (left-hand) end of slidewire S, to the high end of slidewire S, and to the junction of conductor 2I with conductor 22 (at the left-hand end of resistance 23). Conductor B connects with slidewire S through the medium of brush 8*.

Conductors G T S and B extend from sending station I to a suitable selector switch, which is shown at 32 as being of the drum type, as follows: Conductor T extends from the point of juncture of conductors 2| and 22 to a stationary contact 34 on drum 32; conductor S extends from the aforementioned common point 30 to a stationary contact 36 on drum 32; conductor G extends from the common point between conductors 25 and 26 and the left-hand end of slidewire potentiometer S to conductor 33; and conductor 13 extends from the point of engagement of slidewire contactor 8 therewith to the stationary contact 35 on drum 32. Thus, if the member 32 of drum 32 is manually moved from the ofi position thereof illustrated to position 1 the mutually insulated portions 32", 32 and 32 will simultaneously act respectively to bridge the pairs of drum contacts 34, 31, 35, 38 and 36, 39, thereby effecting presetting of circuits respectively including one or more of the aforementioned conductors T S G and B for completion upon manual operation of an associated selector switch 48 (which may also be of the drum type) from its off position in one direction to a position designated Standardize or in the other direction from "oif in sequence to positions designated Level and Temp.

For example, with drum 32 moved to its position 1, and with switch 40 in Standardize position, the conductors G and S are connected, in series with an amplifier system of known form, across the slidewire S of the common receiving potentiometer; and at the same time a mechanical coupling 4| is completed between the motor 42, actuated from the amplifier system, and the contactor 43 associated with resistance 44 to effeet adjustment or variation of the current supplied from a battery to said receiving potentiometer .8 In the standarizing operation the current supplied by battery is adjusted so that the voltage drop across the receiving potentiometer slidewire S will be exactly equal to the voltage drop across the sending slidewire potentiometer S.

More particularly, the circuit connections for said standardizing operation may be traced from the left-hand, or low end of slidewire S, by conductors G and 33 to the left-hand, or low, end of slidewire S and from the right-hand, or high, end of slidewire S, by conductor S through contacts 36 and 39 (then bridged), by conductor 46 through contacts 47 of switch (which contacts are then closed, as indicated at 41*), conductor 413, to the point 49 in the amplifier system aforementioned. Point 49 is the mid-point of the primary winding of transformer l5. Contacts 5i and 52 connected to the input side of transformer l6 periodically engage vibrator arm to alternately close and open the circuit to lead 53, through contacts 54, then closed, and conductor 55 to the high end of slidewire S Vibrator 58, moving in response to the variation and direction of current fiow from lines L and L in coil St causes any voltage difference between conductors 58 and 53 to alternately cause a flow of current in each part of the input side of transformer l6.

Conductors t8 and 53 enter the amplifier (designated in general by the dotted line rectangle lsil in Fig. 1) in which any impressed direct current voltage applied across conductors 8 and is converted into an amplified alternating current in motor winding 62, 42 whose phase shift, in respect of current flow from lines L L to motor "winding 4%, 42 is related to the direction of the applied direct current voltage across conductors t8 and 53. See, for example, the disclosure in Patent No. 2,113,164, granted April 5, 1938, to Leeds 8; Northrup Co, as assignee of A. J. Williams, Jr. With zero direct current voltage applied to the amplifier I55, motor 52 is restrained against rotation in either direction. With a slight voltage difference motor 42 will run in one direction or the other, depending upon the direction of the applied vol"- age; said relationship being such that motor 42 operates to effect a change in the position of brush '33 to thereby vary the value of the current flow in slidewire S so that the Voltage across S is equalized with respect to the voltage across slidewire S.

As will be readily understood by those skilled in the art, any one of a number of well known alternative types of amplifier and servo mechanism might be employed to effect driving of shaft 56 and shaft section 58 upon engagement of clutch ll, in a manner to reduce the applied direct current voltage to zero.

Also, as aforementioned, during the standardizing operation, an abutment member 51 rigidly attached to a movable part of switch 40 acts through a rod 5? and a pivoted lever 59 to effect engagement of clutch members ll, whereby the shaft portion 56 is driven simultaneously with, and in the same direction as, shaft 56 a, traveling nut 43 carrying the contactor 33, having threaded engagement with shaft portion 56 to effect shunting of more or less of the resistance 44 normally included in circuit with the righthand end of slidewire S A fixed resistance $0 of a suitable value is preferably included in circuit with the active portion of resistance 44.

Motor 42 is provided with a set of windings 42 and 42", which are connected in series with each other across a suitable source of electric current supply, represented by lines L and L in parallel relationship to the secondary winding iii of a transformer 6i, the primary winding of which comprises two sections fil and tl arranged as shown with respect to each other and to a pair of electron tubes $2 and 63 in a well known manner to control the direction and degree of rotation of shaft 56 and the associated shaft portion 56 by motor 42.

With switch 32 in the aforementioned position "1, the level of liquid in the first tank of the group (associated with sending unit i) may be measured and indicated by manually moving switch 40 to the Level position thereof, whereupon the motor 42 will be operated automatically (if necessary) to insure that the voltage drop in the left-hand end portion of sending slidewire potentiometer S between brush 8 and ground 3| is equaled, or balanced, by effecting movement of the brush 55" on the common receiving slidewire potentiometer S to a position corresponding to the position of brush 8 on the sending slidewire potentiometer S. The movement of brush 56 is incident to rotation of shaft 56 in one direction or the other by operation of motor 42.

The circuit connection for said liquid level indicating operation may be traced from the lefthand end of slidewire S, by conductors G and 33 to the left-hand end of slidewirc S and from r the lower end of brush 8 by conductor B through contacts 35 and 38 (which contacts are then bridged by portion 32), by conductor 64 through contacts 65 of drum til (which contacts are then closed, as indicated at 65) conductor 48, to the point 49 in the amplifier system, the relay contactor being engaged with one or the other of the contacts 5!, 52, and from contactor 50 by conductor 53 through contacts 66 of drum 40 (which are then closed, as indicated at 66 and by conductor 5? and slidewire extension 67 thereof to the lower end of brush 55 whose upper and engages the slidewire potentiometer S More particularly, the control of the direction of operation of motor 42 includes a second pair of windings 42 and 42 which are connected in series with each other; one terminal of winding 42 being connected by conductor 68 to the common point Si between the aforementioned primary windings 6 l and 6! of transformer SI, and one terminal of winding als being connected to said common point 6| by conductors 58 and 1B, through condenser ii and conductor 12. The other elements of the amplifier system may be of known form, as illustrated, and the same function in a well known manner. Thus, the anode 62 of the tube 62 is connected to the outer end of winding 61*, and the anode (53 of tube 63 is connected to the outer end of winding 55.

Cathodes 62 and 63' of said tubes are jointly connected through resistance 73 to a conductor 14, which leads in one direction to conductor 59 and in the. other direction, through a battery 75 to one terminal of the secondary winding 36 of transformer 15. The other terminal of winding 16 is electrically connected with the grid 11 of an electron tube 17; the anode of said tube being shown at T! and the cathode thereof being shown at 11*. Anode 11 is connected by conductor 18, through a condenser 19 and conductor 80, with the grids 62 and 63 of tubes 62 and 63, respec- 7 tively. Cathode li is connected to conductor 14.

Condenser 19 also has its right-hand terminal connected by conductor 89 and a resistor Bl with conductor 14; the left-hand terminal of said condenser being connected by conductor 18 through a resistor 82 and a battery 83 with conductor 14. A resistance 84 of suitable value is connected across the terminals of the aforementioned winding "15 of transformer 16.

The float unit 16 i best illustrated in Figs. 2 and 3, and the same consists essentially of at least two floats pivotally connected to each other through the medium of one or more levers or sets of levers. In the preferred form of float unit [6, as illustrated, three floats are employed; the intermediate float being designated by the numeral 85, and the pair of like opposite end floats being designated by the reference numeral 86. Float 85 may be considered as the master, and the floats 86 as the compensators.

The intermediate float 85 has attached to its upper surface a pair of brackets 85*, the perforated upturned ends cf which provide for pivotal connection thereto of the ends of sets of levers 85, as indicated at points 1c in Fig. 2; other ends of said sets of levers 85 being pivotally attached to pairs of brackets 86 at the points m in Fig. 2; said brackets being attached to the upper surfaces of the respective compensator floats 86. The two inner levers 85 of each set are of approximately f-shape or strut form; the adjacent portions thereof being flat, and spaced from each other sufliciently to accommodate therebetween the laminated, or double-thickness, arms designated by the numeral 85. The pairs of inner levers 85 of each set are rigidly attached to one end of the respective arms, as by means of pairs of rivets, as shown at 85 in Fig. 3; and said arms 85 are likewise pivoted at points is, Fig. 2, to rods or shafts 85 which are connected to and alined with the pivot pins in the upturned ends of brackets 85 as shown.

The adjacent ends of arms 85 are provided with openings or eyes (2, 2, Fig. 2) through which equal-length branch end portions i and l of cable I may be passed and tied or otherwise socured, as shown in Fig. 2.

The master float 85 also preferably has rigidly attached to its lower surface a pair of relatively long brackets Bil the downturned end portions of which are perforated to accommodate pins for pivotal support of the adjacent perforated ends of sets of levers 85 as indicated at points k in Fig. 2; the other ends of said sets of levers 85 being pivotally attached to diametrically opposite sides of the enlarged lower end portions of floats 86, as indicated at 86 in Figs. 2 and 3 (points m Fig. 2); the upper and lower sets of pivot It and k on float 85 and m and m on floats 88 being vertically alined under all normal operating conditions.

As best illustrated in Figs. 2 and 3 there is a predetermined fixed relationship between the pivot points It and m, and the points x and z; and under all normal operating conditions the pivot points k will be vertically alined with points 3:, and pivot points m will be vertically alined with points m. Likewise there is a predetermined fixed relationship between the weight and area of master float 85 with respect to the weight and area of each of the like compensating floats 86. The aforementioned relationship of such parts is adapted to provide a given relationship between the action of float unit 16 with respect to cable upon cable I0, whereby the float unit l6 will act to indicate the level 15 of the liquid in the particular tank, notwithstanding variations in the speciflc gravity of the liquid, as an incident to variations in temperature or composition of the liquid.

More particularly the relationship of the parts of float unit 16 is such that if the ratio of the length of each set of levers 85 (including a portion of the respective arm 85) between pivot points z and m, in Fig. 2, to the length of the portion of each arm 35 between pivot points z and m is expressed as equal to a constant L, then the depth of effective submergence of the respective floats 88 must be equal to L times the depth of efiective submergence of the master float 85. The depth of eiiective submergence of each float E5 and 36 depends upon the downward force of the float (consisting of the weight of the float and any additional downward force exerted upon such float) divided by the product of the horizontal cross sectional area of the particular float at the liquid line and the density of the liquid.

By way of example, let it be assumed that the right-hand compensator float 8i: and its associated set of levers 85 85 and arm 85 are removed from the assembly and that the lower end of cable 1 terminates at the point z of the lefthand arm 85 and exerts an upward force of two pounds as an incident to the action of counterweight 9, and drum I l which is tapered in a inanner to compensate for the weight of the cable 7 between drum 8 and said point e; the cable 1 will then exert an upward force of upon pivot point r and a downward force of upon pivot point y; which forces added to the weights of floats 85 and 86 must produce a depth of submergence of said left-hand compensator float 3B which is L times that of the master float 85. In other words, the weight of left-hand compensator float plus divided by the horizontal cros sectional area of said float must equal the weight of master float 85 minus 2L Ll divided by the horizontal cross sectional area of float 85. Any change in density of the liquid will then affect the height of pivot point 1/, carried by float 85, by L times as much as it will the pivot point :t, carried by float 35. Consequently the distance between the point of connection of cable 2' to arm 85, at z and the liquid level IE will remain constant notwithstanding variations in specific gravity of the liquid.

The manner in which a substantially constant upward force upon the float unit I6 is insured may be described as follows: The counterweight Q and the unwound portion of its associated cable it jointly exert a torque equal to the product of the radius of the variable radius drum II at the point where cable Ii? leaves drum H, multiplied by the combined weight of counterweight 9 and the unwound portion of cable Hi. This torque must equal the torque exerted by a preselected constant upward pull of the cable I upon the float l and the counterbalancing action of weight 9 unit [6, plus the weight of the unwound portion of the float cable 1. The latter torque may be defined as: RF[WF+ (HM-HI.) WA], where:

Rr=constant radius of float drum 8;

Wr=desired upward force on float unit l6;

HM=number of feet of unwound cable 1 with float unit 6 in its highest position; and

Hr=nu1nber of feet of unwound cable 1 with float unit it in its lowest position.

WA=weight of cable 1 in lbs./ ft.

The counterweight torque (weight of 9 plus weight of unwound portion of cable it) should then be equal to the torque above-mentioned, and at any one point is equal to: R7)(Vfc-}-.DC); where Rv is the value of the variable pitch (radius); We is the weight of counterweight 9 plus the weight of the unwound portion of cable ill, with the float unit H; in its zero (or highest) position; and DC is the value of the increase in cable weight due to downward movement of float unit it from its highest position. As will be understood, if the cable ID of counterweight 9 is relatively lighter, per unit length, than the cable I of float unit 26, and if the counterweight 9 is relatively heavy, with respect to the desired upward force upon the float unit l6, (which would require a relatively small, but variable, radius drum H, as compared with the drum 8 for the float unit cable 1) and there would be a resultant relatively small change in unwound countercreasing the pitch radius increase rate by the DC value at two points in the operating range; for example, at twenty-five per cent and at seventyfive per cent of full travel of cable IIJ; so that torque compensation will be perfect at these two points and will depart only slightly therefrom at intermediate points. The amount of departure from perfect torque compensation at intermediate points is thereby reduced to an insignificant value.

With reference to the diagrammatic showing of Fig. '7, the following mathematical formulae may be employed to provide for determination of the various dimensions, weight of counterweight 9, weights per unit length of cables 1 and H) which may be combined to provide for accomplishment of the results herein contemplated.

Thus, in Fig, 7 and/or in the following equations, the legends employed are as follows:

W=design lift for float operation (pounds) W1=W+B(C1), where B=feet of cable between float and design pull point, and C1=Weight of cable per ft. (lbs/ft.)

Wz=weight of counterweight 9 in pounds Cz weight per ft. of counterweight cable Ill (lbs/ft.)

ac=distance in it. between datum line and design pull point ro=distance in it. between axis of drum 8 and datum line y==distance in ft. between axis of drum I l and counterweight 53 R=radius of drum 3 in inches r radius of drum l l in inches assuming a condition where 03:0 and y=0, then 10 for balancing of the float unit It and its associe ated cable I, with respect to counterweight 9 and its associated cable H), the values indicated by the following equation are employed:

Integrating:

Substituting Equation 7 for y in Equation 2:

in Equation 7 and the value of given in Equation 10 are employed in solving for the radius of the variable radius drum l l, with the values of certain factors as below set forth. It is to be noted that the departure from a straight line in value of T is extremely small, due to the light weight of the counterweight cable is. With then the foregoing Equations 1 to 10 provide the Ii values indicated following when the distance .r is successively O, 25 and 50 it.

Torque float unit side As with a simple float, the pull of cable 7 will affect the degree of subme'rgence of the compound float IS, an effect which can be reduced by making the floats of relatively large horizontal area, with a corresponding reduced degree of submergence under any given conditions. In a compound fioat of the character herein disclosed economic considerations make it desirable to have at least those positions of the compensator or secondary floats 86 which may move above or below the level It of the liquid of smaller horizontal cross sectional area than the master float 85. It is also desirable that the aforementioned value L should be equal to three or more. That is to say, that the distance between points a: and y in Fig. 2 should be at least three times as great as the distance between points a: and a.

As will be understood by those skilled in the art,

. it is not necessary that the portions of the floats 85 and 86 which never rise above the liquid level or line shall be of any particular form or dimensions in horizontal cross section. Accordingly the bot tom walls of floats 85 and 86 might be made of inverted cone-shape (not shown), so that vapors or gases would not be trapped or held below the respective floats (with a consequent effect upon the buoyancy thereof), and so that the strength of the floats would be increased. Also where the compound float unit is to be employed in conjunction with only very dense liquids, the compensator floats (corresponding to floats 8 53) might be made of such size and shape that the bottom walls thereof would not normally extend below the bottom of the master float 85.

As herein shown, I prefer to use one master float 85 and two like compensating floats 8%. With the construction shown in Figs. 2 and 3 minor errors would theoretically be introduced, due to the variable angle formed by the branch ends I and I between the common point of connection thereof to cable I and the respective points of pivotal connection thereof, at z, a, Fig. 2, to the adjacent ends of arms 85. However, with the length of levers 35 relatively long with respect to the degree of submergence of floats 3 8 the aforementioned variable angle is sufficiently small so that no appreciable error results, even though the branch ends 7 and l of cable 1 are relatively short; provided that the levers 85 are, in a body of liquid of average density, positioned approximately horizontally.

Referring again to Fig. 1, it will be apparent that upon operation of motor 42 in either direction the extension of shaft 56 which is indicated -diagrammatically by the dotted line 5G will simultaneously effect rotation of an indicating disk of circular form, as indicated by the dotted line circle 14; said disk preferably havingen inner circle of numerals and calibrated marks, as indicated by the numeral 95 and the groups of short radial lines I on opposite sides of said numeral 95. In practice said inner circle is provided with twenty numerals (5, 10, 15, etc, up to 100), with twenty-five equal spaces [29 between each pair of indicating numerals. For example,

any maximum level to be encountered.

it may be assumed that each complete rotation of disk I represents one complete rotation of drum 8; so that if one complete turn of cable l' is wound upon or unwound from drum 8 (with the latter having a periphery of, say, five feet) the corresponding complete rotation of disk M will indicate at a given point [2| adjacent window I21 that the liquid level iii in the particular tank has risen or fallen a distance of five feet. In practice the group of tanks in any particular tank farm will usually be of substantially the same height and of the same transverse dimensions. but such an arrangement is not necessary. On the other hand, tanks with which my measuring apparatus may be employed are likely to provide for maximum liquid levels from as low as twenty feet to as high as forty feet, or higher; and accordingly I provide for accurate measurement of More particularly, I provide on disk H a projection (not shown) which is adapted upon each complete rotation of said disk from a given position to effect a step of movement of an associated disk (which may bear the numbers 1 through 10,"

or higher, as represented by the numeral 6" which is in register with the auxiliary window [22 in 1). Thus in the particular setting of the indicating disks shown in 1 the numeral 5 indicates that the level It of the first tank of the group is at six times five feet, or thirty feet, plus ninety-five one-hundredths of five feet, or four and three-fourths feet, so that the level is indicated as thirty-four and three-fourths feet.

If the liquid level should fall exactly five feet the associated disks would be moved accordingly so that the numeral 5 would show in window I22 and the numera 95 would again register with the point or line i2 i at the receiving station It.

When it is desired to measure the average temperature of the liquid in the first tank of the.

group, the rotary switch or drum 32 is allowed to remain in its aforementioned position 1, and switch 40 is moved from the aforementioned Level position to the position marked Temp. (indicating temperature). In this position of switch 40 the contacts 66 and I23 thereof will be closed, as indicated at 66 and I23 in Fig. 1. Under these conditions the voltage drop of thermometer I! (which is equal to the value of the thermometer resistance divided by the sum of the thermometer resistance plus the value of the resistance 23 in series with the thermometer resistance, multiplied by the voltage of the entire slide-wire resistance S) is established between the low (or left-hand) end of the receiving slidewire resistance S and the contact 56' associated with the latter, by automatically effecting movement of said brush through operation of motor 42 as previously described. The disk It (Fig. 1) which is driven simultaneously with brush 56 by motor 42 is calibrated (inner circle I20) to indicate in feet and decimal parts of a foot, and also (outer circle) in degrees of temperature. For such temperature measurement only a limited part of the outer circle of indicating numerals will ordinarily be utilized inasmuch as a major portion of the total drop in the sending slide-wire rheo'stat S under these conditions will be in the series resistor 23.

More particularly, during temperature measurement a circuit extends from the left-hand terminal of battery 21, by conductor 25 to the lower terminal ll of thermometer resistance ll, through the latter and upper terminal H by conductor 2! through conductor T contacts 34 and 31 (which are then bridged by contact block 32') by conductor E25 through contacts !23 (which are then closed, as indicated at I23 by conductor :38 to the point 49 between the primary windings of transformer l5, by one or the other of contacts 5! or 52 to contact 50 and conductor 53, to contacts (which are then closed, as indicated at 6t by conductor 5'6 and extension S'l to contact 56 and the portion of potentiometer rheostat S to the left of said contact, and by conductor 33 to conductor G and ground at 3!. A circuit likewise extends from the aforementioned conductor 2! by conductor 22 and resistor 23 to the common point 39, and thence through the total length of slide-wire resistance S to ground at 3!. The parts of the receiver M will act in the manner aforedescribed to effect operation of motor d2 in a direction and to a degree to accurately indicate, by the position of the outer circle of disk Hi the temperature of the liquid in tank number I.

In Fig. 2 I have shown at 81 a fragment of a cone-shaped roof of a tank adapted to contain a variable quantity of liquid as represented diagrammatically by the liquid level line [5. Roof 8! is provided with an opening of suitable size and shape to accommodate the lower end of a metal housing of suitable form, as shown more or less diagrammatically at 88. Although housing 88 is diagrammatically shown as rigidly and permanently attached to roof 8! as by means of a peripheral weld 89, it is to be understood that in practice such permanent connection will be made between a metal man-hole member, or a relatively large pipe flange, and roof Bl; such man-hole member in turn afiording means by which housing as may be removably attached to the tank, and aifording access to the interior of the tank upon removal of housing 88. In any event, it is desired that housing 88 shall have a gas-tight connection with the tank, in order to save vapors from the liquid in the tank by conventional means, and to prevent such vapors from getting into the compartment in which the respective sending potentiometer rheostat is located. i

Positioned within housing 33 is the aforementioned rotatable drum 8, which is non-rotatably attached, as by means of a set-screw 963, or the like, to the reduced end portion 91 of a metal shaft 9 5, preferably formed of stainless steel. Housing as is provided in the right-hand side wall thereof with an opening 38 to accommodate with a close fit the end portion 92* of a metal member 92 carrying a ball-race member 5-33, between which and a second balhrace member 95, attached to a portion 95 of shaft 53!, a series of ball-bearings 94 are positioned. The portion 82 of member 92 is adapted to accommodate the portion St of the shat with a sufliciently close fit to preis provided with a flange which abuts the inner end of member 92; said flange being peripherally welded to member 82, as indicated at 56 Member 92 is provided with a flange 92 which is seated gas-tightly against the outer surface of housing 88; and said housing is rigidly secured by a multiplicity of screws 91, the shanks of which thread into tapped openings in said housing wall. Flange 92 is provided with a drilled passage 92 which extends vertically downward into communication with the recess 92; a suitable quantity of mercury being inserted to completely fill the remainder of recess 92 and a portion of the length of passage 92 thus providing a gas-tight seal between the interior and exterior of housing 88.

The other end of shaft 9! is provided with shouldered portions Sl and Si the former having attached thereto a ball-race member 98, which cooperates with another ball-race member 99 to accommodate a group of ball-bearings 10H. Member 99 is attached in any suitable manner to a metal member Iill, which is provided with a flange Ull the latter being rigidly attached to a Wall of another housing, a fragment of which is shown at its as by means of a multiplicity of screws 96 like those aforementioned.

Members 92 and I!!! are provided with like tubular portions 92 and Hll extending toward each other; said portions being adapted to telescopically receive the reduced and shouldered opposite end portions of a tube I83, preferably of brass; and said parts are sealed to each other, as by means of the peripheral lines of welding shown at 92 and H Said wall of housing 102 is provided with an opening to accommodate with a close fit the portion liil of member 16!. A metal member is provided with a flange it, which is secured, by screws I 05, or the like, to portion lfll said member being also provided with a tubular portion [E i which affords only a slight amount of rotary clearance for the portion HI of shaft 9|.

A metal member having a flat, circular portion Hit of relatively large diameter, with a centrally located flanged opening [95 whereby the same is slidable onto the aforementioned tubular portion M for partial support by the iatter; portion I06 having a plurality of openings formed therein to provide clearance for the shanks of screws It! which are threaded into tapped openings in the housing wall I02 whereby said portion N35 is retained in a fixed position. Formed integrally with portion I06 is an outwardly projecting cylindrical flange 16 as shown in detail in Fig. 4. The cylindrical surface provided by portions I05 and NW has applied thereto (and heat indurated thereon) a surface layer 568 of suitable thickness composed of a known type of synthetic resinous material. I prefer to employ a so-called polythene resin, which resin is sold commercially under the trade-name of Rac- Lac-Dip. After hardening of the layer of resin it, the same is ground or shaved ofi to provide a smooth cylindrical outer surface of preselected circumference (see Fig. 4); and said layer Hi8 then has formed therein, as by machining, a pair of parallel spiral grooves "38 and H18 of approximately semicircular form in transverse cross section, to accommodate about one-half the respective cross sectional areas of a coiled resistance wire 509 and a coiled conductor Hi In prac ties the parallel coiled wire lat and conductor wit are retained within their respective grooves by means of a suitable cement or adhesive (not shown) Wire lili-i is provided with end terminals lSil and I38", while conductor M39 is provided with a single end terminal it i, to which both ends of the conductor may be assumed to connect. If the device of Fig. 4 were used in a circuit such 15 as shown in Fig. l in lieu of S, 8 and 13 then terminal i311 of wire ltS would be connected to the junction of 26 and G and the terminal [38 to the junction point 30. Conductor H19 would take the place of B and its terminal l3! would be connected to contact 35.

As shown in Fig. 2, the aforementioned tapered drum ll carries a hub portion H, which is adapted to fit onto the outer end of portion Si of shaft 9! and is non-rotatably secured to the latter in a suitable manner, as by means of a set screw H9. Cable H) has one end thereof attached to the small end of drum ll, so that said cable will be wound onto or payed out from the spiral groove ll upon downward or upward movement, respectively, of the compound float it, through the action of weight 9. Also, as aforestated, the gradually increasing diameter or peripheral length of each complete turn of the groove li will serve to compensate for the increased weight of the length of cable I which is unwound from drum 8 as an incident to lowering of the liquid level 15 in the respective tank and for the decreased weight of the length of cable It between weight 9 and drum H.

Drum II has rigidly attached to the inner or large end thereof an insulating plate Hi, as by means of screws or bolts H2; and the outwardly projecting end of plate III has attached thereto a metal bracket N3, the two arms of which extend at substantially a right angle to each other. One arm of bracket H3 completely overlaps the coiled resistor wire Hi9 carried by the stationary member I66, and said bracket arm has riveted or otherwise attached thereto a resilient metal member I it, which is provided at its downwardlybiased forward end with a pair of downwardly bent perforated lugs H 3 and I14 The perforations in lugs H4 and H4 are adapted to accommodate the shank of a pin H5, upon which is rotatably and slidably mounted, between said lugs, a contactor H5 which is in the form of a roller having tapered ends and a cylindrical intermediate portion l [6 which is sumciently narrow to fit between each adjacent pair of turns of the resistor wire IMF, and conductor [09 and thus permit and insure engagement of the tapered end surfaces of contactor H6 with such adjacent turns. As shown, pin H5 may be provided with a preformed head, 53 for example,

and an upset or riveted end H5 whereby said parts are retained in assembled relation. It will be readily seen that contactor H6 is automatically guided, for movement thereof axially of pin H5, in accordance with the degree of rotation, or number of rotations, of drum H; the degree and direction of rotary movement of the latter likewise corresponding to the degree of rise or fall of the liquid level [5.

The bottom wall Ill of the aforementioned housing (H32, Fig. 2) is provided with an openin ill to accommodate, with a rather close fit, the open upper end of a cylindrical metal member or tube N8 of suihcient length and transverse dimensions to provide clearance for weight 9 in all positions of the latter. Member H8 is rigidly attached to wall ill, as by means of the peripheral line of welding ill. The lower end of member H3 is preferably closed, as indicated in dotted lines at i W.

As will be understood by those skilled in the art, after ascertainment and indication of the liquid level and the average temperature of the liquid in each tank individually, the operator at the central station, after making a note of such values, may refer to the usual strapping tables and temperature correction tables for the particular liquid in each tank, whereby the actual liquid content measurement of each tank may be readily and quickly calculated. In practice it is found that when the liquid level and average temperature of the liquid in each tank has been measured individually by use of the apparatus herein disclosed the operator at the central station will have ample time to calculate the actual liquid content of a particular tank while the apparatus is being operated (by manipulation of switches 3-2 and 5G) to effect measurement of another value (liquid level, for instance) in respect of the body of liquid in the next succeeding tank. For this reason a single operator will be able to take frequent or repeated readings of the liquid levels and temperatures of a very large number of individual tanks during any given substantial period of time, without permitting or requiring the apparatus to remain idle during the aforementioned calculations by the operator.

As best illustrated in Figs. 2 and 3, the master float and the compensator floats 85 are referably formed of punched and stamped sheet metal parts. Thus, the top wall 85 of float 85 may consist of a flat sheet metal punching of circular contour; wall 85 having a centrally located clearance opening formed therein, and a nut 85* (Fig. 2) being welded to the inner surface thereof in alinement with said opening. A bolt 85 is threaded into and through nut 85 to extend downwardly a predetermined distance; a second nut 85 being initially located adjacent the head of bolt 85 and the same being finally tightened against the outer surface of part 85 The remainder of float 85 may consist of a punched metal member which is drawn or spun to substantially cup-shape, as shown at 85 in Fig. 2; the parts 85 and 35 being brought together and welded leak-tight to each other around the respective peripheries thereof. With said parts so united, the shank end of bolt 35 will normally just touch the inner surface of the bottom wall f the complete float 85; thus assisting in insur ing against substantial bending or distortion of the bottom and top walls of the fioat as an incident to use thereof in a body of liquid.

The compensating floats 85, 86 will each preferably consist of an inverted cup-shaped upper portion 35, an intermediate portion and a fiat, punched sheet metal bottom wall portion 86 all Of said portions having peripheral edges which overlap, and said edges being peripherally welded to provide leaktight connection therebetween. The top wall of portion 85 of each float 86 is provided with a clearance opening, and a suitable nut is welded to the inner surface of said top wall. Relatively longer bolts are threaded through the respective nuts (like nut 35 in float B5) to insure the desired spacing of the top and bottom walls of floats 86 when completed. Each bolt 86 also preferably has associated therewith a nut (not shown) which acts as a lock-nut against the outer surface of the top walls of floats 86, to prevent accidental loosening of said bolts.

In Fig. 8 I have illustrated diagrammatically a modification, wherein S indicates the sending potentiometer rheostat individual to one of the tanks aforedescribed; the bridging contactor 8 thereof being automatically adjustable in accordance with the level of liquid in the tank selected by the switching means, in the manner heretofore set forth. Included in the circuit is an indicating galvanometer G, which serves to indicate the degree of unbalance resulting from the automatic movement of contactor 8 However, instead of employing the servo mechanism here inabove described for effecting the automatic follow-up adjustment of contactor CB of the receiving potentiometer S said contactor CB is adapted to be manually adjusted to effect the desired balancing of the circuit, with resultant accomplishment of the desired efiect. In a similar manner, I provide a manually adjustable rheostat I35, the purpose of which is to provide for standardization of the common receiving ptentiometer rheostat with respect to each sending potentiometer rheostat (S) prior to ascertainment of the liquid levels in the respective tanks. The batteries 27 and 45 correspond with those bearing like numerals of reference in Fig. 1.

In Fig. 9 I have illustrated diagrammatically, in greater detail than in Fig. 1, the relationship and manner of operation of the common receiving potentiometer rheostat S with respect to each sending potentiometer rheostat S. The legends applied to Fig. 9 show that, in the form of my invention herein illustrated, if the resistance value of sending potentiometer rheostat S is 200 ohms from one end thereof to the other, a resistance R is preferably employed at the lefthand end thereof; said resistance R having a value equal to one-half of one per cent (1 ohm) of the value of resistance S, from the left-hand terminal to 0; and a resistance R between the point 10 and the right-hand terminal also equal in value to one-half of one per cent (1 ohm) of the value of resistance S. The common receiving potentiometer rheostat S is shown as comprising eighteen coils, each having a resistance value of ten ohms; said rheostat S having a resistance value of ten ohms from 0 to l; a resistance R having a value of five per cent of the resistance of S from #9 coil to 0 coil; and a resistance R having a value of five per cent of the resistance S from #1 coil to 0 coil.

In operation, when contact CB goes below zero on S or above 1 on limit switches (not shown) function to move the contactors CC-l and CC-2 jointly toward the right or left in steps. For example, as shown in Fig. 9, sender contactor CA is at 2.45; that is to say, the voltage drop in sender rheostat S from GR (ground) to contactor CA is one-half of one per cent plus 24.5 per cent of the voltage drop from zero to 10. On the receiving rheostat S when balanced, the voltage drop from GR to contactor CC-l is twenty per cent plus one-half of one per cent plus four and one-half per cent of the voltage drop across ten times the resistance value of S If CA should move to 6.5, contactor CB would go to right-hand. end of S and CC-l and CC-2 would then move step-by-step toward the left until they rest upon contacts 6, 5; whereupon C'Bdvould start moving toward the leftaway from the limit switch, stopping and CC-Z from moving farther, and move until a reading of 5.50 is obtained. The operation of this mechanism under various other conditions will be apparent to those skilled in the art.

I claim:

1. In a distant liquid level indicating apparatus, combination, a potentiometer type sending rheostat, a source of current supply for said rheostat, a slider contact forming part of said potentiometer rheostat whose position on said rheostat is indicative of the level of a body of liquid, a receiving potentiometer rheostat including a source of current supply therefor, a third rheostat in circuit with said receiving potentiometer rheostat for adjusting the current flow through the latter, a motor operated means for driving the slider of said last mentioned potentiometer rheostat either individually or jointly with said third rheostat in one direction or the other, an amplifier syst m responsive to minute difierences in potential between preselected corresponding points on the sending and receiving potentiometer rheostats for efifecting energization or said motor operated means to cause movement thereof in one direction or the other according to the sense or direction of the instantaneous potential difference, electric switching means selectively operable to one position for electrically connecting parts of said sending potentiometer with corresponding parts of the receiving potentiometer in series with said amplifier and effecting mechanical coupling of said third rheostat to said receiving potentiometer for joint operation. by said motor operated means in a manner to establish the same potential across the receiving potentiometer rheostat as that existing on the sending potentiometer rheostat and operable to a second position to connect the sliders of said sending and receiving potentiometer rheostats in series with said amplifier.

2. In a system for indicating the level and temperature of a liquid in a tank, in combination, a sending potentiometer rheostat having a slider contact whose position is indicative of the level of a body of liquid, a source of current supply for said rheostat, a resistance type thermometer for sensing the temperature of the body of liquid connected in parallel circuit with the resistance element of said rheostat, a receiving potentiometer rheostat, a source of current supply for the last mentioned rheostat, a third rheostat for adjusting the current flow through the resistance element of the receiving rheostat, electric motor operated means for driving the slider of said receiving rheostat in one direction or the other, said motor operated means including connectable driving connections afiording drive of the slider of said third rheostat concurrently with that of said receiving rheostat, and switch means selectively operable to one position to complete said driving connections and connect in circuit an end of the resistance element of said sending rheostat with a corresponding end of the resistance element of said receiving rheostat to afiord balancing of the potential drops across the resistance elements of said sending and receiving rheostats, to a second position to connect together in circuit the sliders of said sending and receiving rheostats to aiTord indication of liquid level, and to a third position to connect said resistance type thermometer in circuit with the slider of said receiving rheostat, said motor operated means further including amplifying means having input terminals included in the aforementioned circuits established by said switch means and providing for operation of the motor in a direction and to a degree according to the direction and magnitude of the voltage across said input terminals.

3. In a system for indicating the level and temperature of a liquid in a tank, in combination, a battery, a sending potentiometer rheostat having a slider contact Whose position is indicative of the level of a body of liquid and having a resistance element which is connected to ground at one end thereof with the low potential terminal of said battery and which is connected at its other end to the other terminal of said battery, a resistance type thermometer for sensing 1e temperature of the body of liquid connected in parallel with said battery and said resistance element of said sending rheostat, a receiving potentiometer rheostat, a third rheostat, a second battery connected in series with the resistance element of said third rheostat across the resistance element of said receiving rheostat, said resistance element of said receiving rheostat having the end thereof connected to the low potential terminal of said second battery connected to ground, electric motor operated means for driving the slider of said receiving rheostat in one direction or the other and including commutatable driving connections afiording drive of the slider of said third rheostat concurrently with that of said receiving rheostat, and switch means selectively operable to one position to complete said driving connections and electrically connect in circuit said other end of the resistance 'element of said sending rheostat with the corresponding end of the resistance element of said receiving rheostat to afiord balancing of the potential drops across the resistance elements of said sending and receiving rheostats, to a second 20 position to connect together in circuit the sliders of said sending and receiving :rheostats to afford indication of the level of the liquid at said receiving rheostat, and to a third position to connect said resistance type thermometer in circuit with the slider of said receiving rheostat to aiTord indication of the temperature of the liquid, said motor operated means further including amplifying means having input terminals included in the aforementioned circuit established by said switching means and providing for operation of the motor in a direction and to a degree depending upon the direction and magnitude of the voltage across said input terminals,

References Cited in the file of this patent UNITED STATES PATENTS 

